Mobile phones, such as smartphones, are normally assigned a phone number through which users can make and receive telephone calls using a wireless cellular network. Some cellular network operators allow other network-connected user devices, such as tablets, televisions, wearable devices (e.g., smart watches), etc., to be associated, as secondary devices, with the phone number or account of a primary mobile device (e.g., the user's smartphone). Telephone calls made to the phone number may then be received, and potentially answered, at either the primary and secondary devices.